The present invention relates to a method of cleaning the inner surfaces of gas turbine that accumulate deposits, which can negatively affect the performance of the turbine. More particularly, the present invention relates to a method of cleaning gas turbine compressors using crushed, solid material that undergoes sublimation, such as dry ice, which can be used in cold weather conditions, poses no risk of ice formation, clogging of cooling hole passages, or degrading the emissions from the turbine.
As gas turbine compressors operate, deposits accumulate on the inner surfaces of the compressor. Such deposits, known as fouling, can reduce the operating efficiency and output power, and result in an increase in fuel consumption. As a consequence the compressors must be cleaned continuously or repeatedly.
Traditionally, solid particles, such as rice or ground nutshells have been used to clean deposits from the inner surfaces of gas turbine compressors. However, the use of such solid materials has numerous drawbacks. First, such particles are accelerated into the interior of the compressor by high-pressure air. As a result, the particles can cause damage to the inner surfaces and the internal compressor parts. Second, such solid particle abrasives can clog cooling passages. Third, any particulate matter remaining in the compressor after cleaning may become ash when burned in the combustors resulting in potentially harmful emissions. Fourth, spent abrasive material needs to be disposed of after cleaning. However, if the abrasive solid particle material is an environmental hazard, it may be difficult to dispose of.
To overcome some of the foregoing drawbacks of solid particle compressor cleaning, water, has been used as a cleaning agent that is pumped into the compressors. However, such water washing has its own inherent drawbacks discussed below.
Referring to FIG. 1, a traditional water washing system is illustrated. The turbine 10 has a bellmouth 12 that faces the inlet plenum 14. Water is supplied through supply lines 18 to pumps 24 and 20. Pump 20 is connected to an on-line manifold having nozzles 16 positioned just above or upstream of the bellmouth 12. Similarly, the pump 24 is connected to an off-line manifold having nozzles 22 positioned just above or upstream of the bellmouth 12.
Water cleaning agents can be used while the turbine is not in operation, known as off-line cleaning, or while the compressor is running, known as on-line cleaning. Off-line cleaning has an advantage in that it is more effective at removing the deposits. On the other hand, while off-line the compressor is not generating power, at a significant loss to the operator. Although on-line cleaning can be performed while the compressor is running, usually at a reduced level of performance, it is less effective at removing the accumulated deposits.
Water is not as effective as solid particles in cleaning the deposits from the inner surfaces of the compressor. Furthermore, water can be used only when certain environmental conditions are met. In particular, when ambient temperatures are below 50xc2x0 Fahrenheit, in this environment there is a strong likelihood that the water will freeze, thereby creating ice formations that can damage the compressor, such as inlet guide vanes (IGVs). These ice formations can result in severe damage to parts such as the IGVs, which are expensive to manufacture and replace. As is the case with traditional solid particle cleaning, water may present an environmental hazard that presents disposal problems.
In an attempt to increase the temperature range within which water can be used, additives have been mixed with the water to lower its freezing point. However, such additives produce emissions that do not comply with local and federal codes and requirements concerning the handling of hazardous materials and environmental regulations.
The foregoing and other deficiencies of the conventional technique are addressed by the method of cleaning gas turbine compressors according to the present invention. An exemplary method of cleaning gas turbine compressors uses crushed, solid material that undergoes sublimation. In one aspect of the invention the solid material is dry ice, which can be used in cold weather conditions. Dry ice poses no risk of ice formation, clogging of cooling hole passages, or degrading the emissions from the turbine.